A transmission mechanism included in a conventional vehicle drive device is capable of changing the speed range between a low range (L) and a high range (H) in response to, for example, a driver's operation of a range changing switch and the like (see, for example, Patent Literatures 1 and 2).
The transmission mechanism generally changes the range in a state in which an output shaft of the transmission mechanism is being stopped, for example during a vehicle stop. The transmission mechanism changes the range by, for example, sliding a clutch sleeve in the direction of the output shaft thereof and thereby connecting the clutch sleeve to a low gear or a high gear. The clutch sleeve is integrally rotatably and axially movably mounted externally around the output shaft of the transmission mechanism.
The low gear and the high gear each have, on the corresponding outer circumference thereof, a plurality of teeth (splines) that are circumferentially arranged at regular intervals. The clutch sleeve has, on the inner circumference thereof, a plurality of teeth (splines) that can be engaged with the teeth (splines) of the gears. When the inner teeth (splines) of the clutch sleeve are engaged (spline-fitted) with the outer teeth (splines) of the low gear or the high gear, the clutch sleeve is connected to the low gear or the high gear.
When the clutch sleeve is slid in one direction along the shaft to be connected to the low gear, a power transfer path is established through which low-speed rotational power is transmitted from the low gear and the clutch sleeve to the output shaft, thereby the “low range” is established.
When the clutch sleeve is slid in the opposite direction along the shaft to be connected to the high gear, a power transfer path is established through which high-speed rotational power is transmitted from the high gear and the clutch sleeve to the output shaft, thereby the “high range” is established. Note that when the clutch sleeve is in neutral position in which the clutch sleeve is connected neither to the low gear nor to the high gear, a neutral range state is established in which rotational power is not transmitted.
Patent Literature 1 discloses, in paragraphs [0014]-[0016], a vehicle transfer in which a power gear and a sleeve that is spline-fitted to the power gear are disposed between a low speed gear and a high speed gear, and in which the sleeve is spline-fitted to the low speed gear to establish a low speed mode and the sleeve is spline-fitted to the high speed gear to establish a high speed mode.
Patent Literature 2 discloses, in paragraphs [0014]-[0017], a vehicle sub-transmission in which an input gear and a sleeve that is spline-fitted to the input gear are disposed between a low speed side gear and a high speed side gear, and in which the sleeve is spline-fitted to the low speed side gear to establish a low speed mode and the sleeve is spline-fitted to the high speed side gear to establish a high speed mode. Patent Literature 2 also discloses that, in sliding the sleeve, energy is stored for moving the sleeve from a high speed side to a low speed side, or from the low speed side to the high speed side, thus the sleeve is slid with considerable energy.